Defrosting



' April 30, 1935. M. A.' HlRscHL DEFROSTING Filed sept. 2o. 1930 Jgd-Patented Apr. 30, 1935 UNITED STATES PATENT OFFICE 8 Claims.

rived from heat, as from a gas flame, or where the apparatus is operatedby mechanical power.

Power refrigerating apparatus, regardless of the kind of power used, isordinarily provided with a chilling unit which may -be a coil, tank, orany other body which is cooled and thus serves to cool the air in thecooling compartment of the refrigerating apparatus.

In apparatus of this kind, the chilling unit in cooling the surroundingair usually causes condensation of water on said unit, whichcondensation freezes. There is accordingly built up on the chilling unita coating of ice which keeps getting thicker until it interferes withthe proper operation of the apparatus. Heretofore, when this occurred,it has been the custom to shut oif the power, permitting the apparatusto warm up until the coating of ice melts off of the chilling unit. Thisis commonly referred to as defrosting.

One of the features of my invention is the provision of mechanism forautomatically defrosting the chilling unit whenever the coating of icereaches a pre-determined thickness.

I have also provided means for automatically turning on the power afterthe defrosting is completed.

'I'he invention disclosed herein is an improvement on that shown in myco-pending application, Serial No. 374,134,1i1ed June 27, 1929.

In that form of device embodying the features of my invention shown inthe accompanying drawing,-

Figure 1 is a View in front elevation of a refrigerator; Fig. 2 is asimilar enlarged view of the defrosting mechanism; Fig. 3 is a viewsimilar to Fig. 2 showing parts in section; and Fig. 4 is a diagrammaticView.

Since my invention may be embodied in a variety of forms, it seems bestto state at the outset the general features thereof. Broadly speaking,it may be stated that I make use of the formation of the ice on thechilling unit to shut oi the power. When the power is shut off, the icemelts` After the last of the ice is gone, there will be a rather rapidrise of temperature in the refrigerating compartment and I make use ofthis, operating through a suitable temperature-controlled member, toagain turn on the power. In this manner,

the defrosting is effected automatically whenever the ice in thechilling unit reaches a predetermined thickness. After the ice has allmelted off and the defrosting is completed, the power is automaticallyturned on again. 5

There are several ways in which the thickening coat of ice may beutilized to shut off the power. Broadly speaking, my inventioncontemplates the use of a control member adjacent the chilling unit,said member adapted to be engaged by the coating of ice forming on thechilling unit when said coating reaches a pre-determined thickness.There is also a connection betweeny the control member and the power forthe refrigerating apparatus, and means of some kind operated by loengagement of the ice coat with the control member for shutting off saidpower.

Merely by way of example, and in order to show some particular apparatusembodying my invention, I have shown certain apparatus in theaccompanying drawing. I shall describe such apparatus now more indetail.

As shown ink Fig. 1, IU may indicate an automatic refrigerator, hereshown as the type operated by electricity, current therefor beingsupplied through the wires Il, II. Numeral I2 indicates the chillingunit in the refrigerator. This is here shown as being box-shaped and isof a v type now in common use in small domestic refrigerators. Themechanism inside of the box need not be shown as this is well known inthe art. It will suiice to say that the box I0 contains some suitablemechanism by which current supplied through the wires II, II will keepthe chilling unit I2 cold so that the air in the refrigerator I0 is keptcold. I am referring to apparatus of this kind, in which the chillingunit I2 is cold enough to freeze condensation of water on it so thatthere is built up on it an ice coating.v

In Fig. 3, the chilling unit I2 is shown and the ice coating that buildsup thereon in use is indicated by I3. The particular object of myinvention is the provision of means for automatically ,j shutting offthe power when the ice coating I3 reaches a pre-determined thickness sothat the apparatus will warm up and permit the ice coating to melt ofi'of the chilling unitI I2, thus defrosting the same. I preferably provideunder the chilling unit I2 a drip pan I4 to receive the water from theice cake I3 as it melts off. 'I hls water may escape from the pan IIIthrough the drain pipe I5 and I preferably provide thereon a suitabletrap I6 to make a liquid seal in the pipe. The

lunit I2, and point out adapted to contact end of the drain pipe I5, asindicated by I1, may lead to a sewer.

I shall now describe more in detail the mechanism for automaticallydefrosting the chilling the improvements over the mechanism shown in myco-pending application above referred to. In this case, I providev acontrol member adjacent the chilling unit adapted to be moved by contactor substantial Contact of the ice with it; that is by the lowering oftemperature when the ice touches it, or comes near it. The movement ofthe control member serves to shut off the power. It is to be noted,however, that even if the ice does not touch the control member, or,touching it, does not move-it, the lowering of temperature in theVicinity of the control member by the approaching ice will shut off thepower. In the case here shown, this shutting oi of the power is effectedby movement .of the control member; but it is obvious that the realcause of the shutting off of the power is the lowering of temperaturecaused by the approaching ice. In the form here shown, the controlmember is indicated by I8 and the same is a bi-metallic .strip adaptedto be curved, as shown on Fig. 3, by a lowering of temperature. That is,at the ordinary temperature of the icebox, when the same is in use, butbefore there is any substantial 'amount of ice on the unit I2, the stripI8 may be substantially straight, as shown in Fig. 2. When the ice getsvery close to it or even touches it, as shown in Fig. 3, the lowertemperature caused by the proximity of the ice will cause the lever I8to curve, as shown in Fig. 3. The lever is so arranged that a loweringof temperature causes it to curve away from the ice, as shown.Consequently, the ice will follow it as it thickens.

The upper end of the control member I8 is suitably ,supported in abracket I9. Suitable mechanism is provided so that as the member I8curvesinto the position shown in Fig. 3, it will shut off the power.This mechanism includes a lever pivoted at 2| carrying a. horizontal arm22 provided with pins 23 and 24 between which the lower end of thebi-metallic control lever I8 lies. The upper end of the-lever 20 ispivotally attached to a pin 25 adapted to engage a toggle switch lever26. When the switch lever is in the dotted position shown in Fig. 3, itmakes contact with the contact point 21, thus completing a circuitthrough the wires 28 and 29 which are a part of the power circuit, asshown in Fig. 4. When the bi-metallic member I8 bends into the positionshown in Fig. 3 by the formation of ice, the lever 20 rocks -to push thepin 25 against the switch arm IB to throw it into the position shown bysolid lines in Fig. 3, thus breaking the' circuit and shutting off thepower.

I may also provide means for automatically closing the switch after thedefrosting has been completed. Such means, for example, may include atemperature-responsive element such as a diaphragm orsylphon 30 with aprojection 3I with the upper end of the lever 32 pivoted at 33. Rockingof the lever 32 will operate through the-pin 3l to throw lthe switch I5from its open postion, as shown by the solid lines in Fig. 3, to itsclosed position, as shown by the dotted lines in Fig. 3. As long asthere is any melting ice, the temperature in the refrigerator willremain relatively low. As soon as the last of the ice is gone, therewill be a relatively rapid rise in temperature and the diaphragm orsylphon 30 can be so adjusted that shortly after this rapid risecommences, the same will expand to rock the lever 32 to` close theswitch I6.

There is a diagrammatic view of the wiring in Fig. 4, in which it willbe seen that the power wires II, II lead through the switch I5 on theirway to the compressor and other refrigerating mechanism in the box. Thedetails of this need not be shown, but all of this apparatus isindicated, in general, in Fig. 4 by the numeral 35.

While I have shown and described certain embodiments of my invention, itis to be understood that it is capable of many modifications. Changes,therefore, inthe construction and arrangement may be made withoutdeparting from the spirit and scope of the invention as disclosed in theappended claims, in which it is my intention to claim all noveltyinherent in my invention as broadly as permissible, in view of.the priorart.

What I regard as new, and desire to secure by Letters Patent, is:

l. In an electrical refrigerator having an evaporator, means forcirculating a refrigerant through the evaporator including a motor, aswitch in the current supply line to said motor, a bracket carried bythe evaporator, a housing for the switch carried by said bracket, abimetallic member carried by the bracket adjacent the evaporator, meansoperatively connected with the free end of the bimetallic member andactuated thereby to open said switch, and a thermal responsive elementmounted on said housing and operatively connected to the switch to closethe same upon arise in temperature.

2. In an electrical refrigerator, the combination with the evaporator ofa bracket mounted on said evaporator, a switch housing carried by thebracket, a spring-tensioned switch member mounted in the housing, a linewire terminal car- 'ried by the housing for said spring-tensioned switchmember and an electrical connection for said spring tensioned switchmember, a bimetallic actuator for the switch adapted to open the sameupon the occurrence of predetermined ice conditions at the evaporator, athermal responsive element mounted on said housing and operativelyconnected with said spring-tensioned switch member to bring the same toa closed position upon a rise in temperature.

3. In an electrical refrigerator, an evaporator, motor driven means forcirculating a. refrigerant in the evaporator, defrosting means includinga switch in the current supply line to said motor driven means, abimetallic switch actuator spaced from thc evaporator and directlyexposed to the ice formation thereon to be energized by the propinquityof said ice formation to open said switch.

4. In an electrical refrigerator, an evaporator. motor driven means forcirculating a refrigerant in the evaporator, and defrosting means forthe evaporator including a switch in the current supply line to themotor, a bimetallic member mounted at one end in a fixed positionwith-reference to the evaporator and having its free end directlyexposed to and adapted to be energized by propinquity of the iceformation on the evaporator, a connection between said member and saidswitch, and a thermal-responsive element effective upon a rise intemperature to close said switch.

5. In an electrical refrigerator, an evaporator, motor driven means forcirculating a refrigerant `through the evaporator, and defrosting meansfor the evaporator including a switch in the current supply line to saidmotor driven means, and control means for said switch; said controlmeans including a temperature responsive actuator elef ment for openingsaid switch, said element being t located adjacent the evaporatorwhereby it may be energized by lowering of its temperature due to theproximity of ice forming on the evaporator, and said element being soarranged that movement resulting vfrom its energization by theapproaching ice will be away from the evaporator to insure fulloperating movement of the element.

6. In an electrical refrigerator, an'evaporator, motor driven means forcirculating a refrigerant through the evaporator, and defrosting means'for the evaporator including a switch in the current supply line to saidmotor driven means, and

. control means for said switch; said control means motor driven meansfor circulating a refrigerant through the evaporator, and defrostingmeans for the evaporator including a switch in the current supply lineto said motor driven means, and control means for said switch saidcontrol means including a temperature responsive actuator element foropening said switch, said element being located adjacent the evaporatorwhereby it may be energized by lowering of its temperature due to theproximity of ice forming on the evaporator, and said element being soarranged that movement resulting from its energization by theapproaching ice will be away from the evaporator to insure fulloperating movement ofthe element; and thermal responsive meansresponsive solely to temperature conditions at the evaporator forreturning the switch to closed position.

8. In a control for refrigerators having a cooling unit operated betweenpredetermined temperature limits, means responsive to temperaturechanges adjacent the cooling unit for modifying one of said temperaturelimits to produce a temperature at the cooling unit above the meltingpoint of ice to eifect defrosting of the cooling nit, and a thermalbellows responsive solely tov temperature conditions manifested adjacentthe cooling unitv to restore the same to operation within predeterminedtemperature limits after defrosting.

MARCUS A. HIRSCHL.

